The performance demands on server computer systems, desktop computers, personal digital assistants (“PDA's”), cellular telephones and other electronic devices have led to substantial demands for improved microprocessor performance, for example, measured in clock speed. Power is typically supplied to a microprocessor from a fixed 12V supply rail using a point of load converter or voltage regulator module (“VRM”). In order to supply a fast transient current response, as required by the microprocessor, converter frequencies have been increased to over 1 megahertz (MHz) and, in many cases, multiphase designs have been adopted.
Next generation microprocessors operate at voltages approaching 1 volt (V) and at escalating frequencies. Current requirements are increasing rapidly, increasing the need for very fast transient response. Since 1999, transient response has increased from 20 A per microsecond to about 325 A per microsecond, and is projected to grow to 400 A per microsecond within a year. To address challenges, for example, to shrink the large capacitor banks that would otherwise be required, buck converters must operate at high frequencies, above the 1 MHz range. At such high frequencies, switching losses become critical due to PCB trace inductance and power package parasitics. This has led industry experts to believe that an integrated solution is needed to reach such high switching frequencies.
Prior art semiconductor device packages are produced with a variety of configurations. One such configuration is shown in FIG. 1.
Referring to the drawing figures in which like reference numerals refer to like elements, there is shown in FIG. 1 a prior art semiconductor device package 10 that includes a molded housing 12 which has disposed therein a semiconductor power switching device (not shown). The electrodes of the power semiconductor switching device contained within molded housing 12 of semiconductor device package 10 are electrically connected to respective external leads. Typically, at least one external lead serves as an input lead 14, while another external lead functions as an output lead 16. Other external leads may function as ground connection 18, a control lead 20 for carrying a control signal, and a (Vcc) lead 22.
Operating power MOSFET devices over 1 MHz poses challenges to existing power electronic packages (e.g., D-PAK, D2PAK and the wirebonded SO-8 devices).
It has been found that external leads, such as the ones included with semiconductor device package 10 of FIG. 1, exhibit increased resistance at high RF operating frequencies, and particularly at frequencies greater than about 1 MHz. It is believed that the increase in resistance at high RF frequencies is due to skin effect, a phenomenon which causes the flow of carriers to move toward the exterior surface of the external leads. Skin effect is an electromagnetic phenomenon in which current flowing through a material of a given cross sectional area is confined to the perimeter of that area, especially at elevated frequencies. The skin effect restricts the current to a small cross-section of external leads, thereby increasing the overall resistance of the semiconductor device package and making it less suitable for high frequency applications.
It is, therefore, desirable to have a semiconductor device package that does not exhibit the increased resistance in its external connections due to the skin effect.